Technical Field
Exemplary aspects of the present disclosure generally relate to an image forming apparatus, such as a copier, a facsimile machine, a printer, or a multi-functional system including a combination thereof.
Related Art
In an image forming apparatus that employs an electrophotographic method, a belt shaped image bearer bearing an image contacts a transfer device opposed to the image bearer to form a transfer nip as a transfer portion, thereby transferring the image onto a recording sheet in the transfer nip. During the transfer process in the transfer portion, the transfer portion is sometimes supplied with a transfer bias (which is also referred to as a superimposed bias), in which an alternating current (AC) voltage as an alternating current (AC) component is superimposed on a direct current (DC) voltage as a direct current (DC) component. When the linear velocity, which is the moving speed of the image bearer, is lower than a normal linear velocity, the recording sheet takes more time in passing through the transfer nip. In this case, if a value of the applied transfer bias remains the same as at the normal linear velocity, toner is electrically charged for longer time, resulting in the toner being excessively transferred onto the recording sheet.
Hence, for example, a configuration is proposed in which, when the linear velocity of the image bearer is decreased, the amount of the DC voltage in the superimposed voltage is reduced without changing the amount of AC voltage in the superimposed voltage.